Abstract

A tomographic scheme is presented that ingests ocean acousticmeasurements into an oceanmodel using data from bottom-mounted hydrophones. The short distances between source-receiver pairs (1–10 km) means arrival times at frequencies of 8–11 kHz are readily detectable and often distinguishable. The influence of ocean surface motion causes considerable variability in acoustic travel times. Techniques are presented for measuring travel times and removing the variability due to surface waves. An assimilation technique is investigated that uses differences in measured and modeled acoustic travel times to impose corrections on the oceanographicmodel. Equations relating travel time differences to oceanographic variables are derived, and techniques are presented for estimating the acoustic and oceanmodel error covariance matrices. One test case using a single source-receiver pair shows that the tomographic information can have an impact on constraining the solution of the ocean circulationmodel but can also introduce biases in the predictions. A second test case utilizes knowledge of a bias in a model-predicted variable to limit grid cells that are impacted by the tomographic data. In this case, using the tomographic data results in significant improvements in the model predictions without introducing any biases.